#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>

int main()
{
	int m = 0, f = 1, i;
	for (i = 1; i <= 10; i++)
	{
		m += i * f;
		f = -f;
	}
	printf("%d\n", m);
	return 0;
}